Telephone accessory

Abstract

An apparatus for use with a telephone including, in one embodiment, a detector for detecting when the telephone is in an off-hook condition and disconnect circuit for eliminating the off-hook condition when the off-hook condition is caused by the telephone so that phone calls may be received by the line. An alarm responsive to the detector produces a warning of the off-hook condition if another phone on the line is off hook.

What is claimed is: 
     
       1. An apparatus for use with a telephone that is electrically connected to a phone line, the apparatus comprising: a detector for detecting when an off-hook condition exists on said phone line, and   a disconnect circuit responsive to the off-hook detector for eliminating the off-hook condition when said off-hook condition is caused by said telephone being in an off-hook mode.   
     
     
       2. The apparatus of claim 1 wherein the disconnect circuit electrically disconnects the telephone from the phone line so as to eliminate the off-hook condition caused by the telephone being in an off-hook mode. 
     
     
       3. The apparatus of claim 2 wherein the telephone causes the off-hook condition by adding a load to the phone line and wherein the off-hook detector operates by detecting the presence of the added load on the phone line. 
     
     
       4. The apparatus of claim 3 wherein said disconnect circuit electrically disconnects the telephone from the phone line by disconnecting the load from the phone line. 
     
     
       5. The apparatus of claim 1 wherein the telephone is a cordless phone that is electrically connected to the phone line through a base station, the cordless phone having a talk mode that results in an off-hook condition on the phone line and a standby mode that does not result in an off-hook condition on the phone line, and wherein the disconnect circuit eliminates the off-hook condition by placing the cordless phone in the standby mode. 
     
     
       6. The apparatus of claim 5 wherein the off-hook detector detects that the off-hook condition exists in the phone line by detecting that the cordless phone is in the talk mode. 
     
     
       7. The apparatus of claim 1 wherein the off-hook detector detects the presence of the off-hook condition on the phone line by monitoring a line voltage across said phone line. 
     
     
       8. The apparatus of claim 7 wherein the off-hook detector detects the presence of the off-hook condition on the phone line by determining that the line voltage has dropped below a predetermined threshold. 
     
     
       9. The apparatus of claim 1 wherein the disconnect circuit further comprises a line activity detector for detecting when the phone line is in an inactive off-hook condition. 
     
     
       10. The apparatus of claim 9 wherein a phone system sends a warning signal over the phone line to indicate that the phone line has been in an inactive off-hook condition for a predetermined length of time and wherein the line activity detector detects the warning signal. 
     
     
       11. The apparatus of claim 10 wherein the warning signal includes a plurality of tones and wherein the line activity detector operates by detecting one of said plurality of tones. 
     
     
       12. The apparatus of claim 1 wherein the telephone has an on-hook state and an off-hook state, the off-hook state causing the off-hook condition on the phone line, the apparatus further comprising a testing circuit for detecting when the telephone is in the on-hook state. 
     
     
       13. The apparatus of claim 12 further comprising an override circuit responsive to the testing circuit for resetting said disconnect circuit when the telephone is placed back in the on-hook state. 
     
     
       14. The apparatus of claim 2 further comprising a ring monitor circuit for indicating the presence of an incoming call over the phone line while the phone is disconnected from the phone line. 
     
     
       15. The apparatus of claim 1 further comprising a visual indicator responsive to the off-hook detector for indicating when there is an off-hook condition on the phone line. 
     
     
       16. The apparatus of claim 1 wherein another telephone may be connected to the phone line and wherein the apparatus further comprises an alarm responsive to the off-hook detector for indicating when the off-hook condition is caused by the other telephone 
     
     
       17. The apparatus of claim 1 adapted as a module to be plugged into a phone outlet. 
     
     
       18. An apparatus for use with a telephone that is electrically connected to a phone line, there possibly being another telephone connected to the phone line, the apparatus comprising: an off hook detector for detecting when an off-hook condition exists in said phone line,   a line activity detector responsive to the off-hook detector for determining if the phone line experiencing the off-hook condition is inactive, and   an alarm responsive to the line activity detector for indicating that the phone line is in an inactive off-hook condition.   
     
     
       19. The apparatus of claim 18 wherein the alarm produces an audible alarm signal. 
     
     
       20. The apparatus of claim 18 wherein the alarm produced a visible alarm signal. 
     
     
       21. The apparatus of claim 18 wherein a phone system sends a warning signal over the phone line to indicate that the phone line has been in an inactive off-hook condition for a predetermined length of time and wherein the line activity detector detects the warning signal. 
     
     
       22. The apparatus of claim 21 wherein the warning signal includes a plurality of tones and wherein the line activity detector operates by detecting one of said plurality of tones. 
     
     
       23. The apparatus of claim 18 further comprising a reset circuit for disabling the alarm if the off-hook condition is caused by the other phone. 
     
     
       24. An apparatus for use with a telephone that is electrically connected to a phone line, the telephone causing an off-hook condition on said phone line when in an off-hook state, the apparatus comprising: a detector for detecting when the off-hook condition exists on said phone line, the off-hook detector detecting the presence of the off-hook condition on the phone line by monitoring a line voltage across said phone line,   a line activity detector responsive to the off-hook detector for detecting when the phone line is in an inactive off hook condition, the line activity detector operating by detecting a warning signal sent by a phone system over the phone line,   a disconnect circuit responsive to the line activity detector for disconnecting the telephone from the phone line when the inactive off-hook condition is detected,   a testing circuit for detecting when the telephone is in the on-hook state, and   an override circuit responsive to the testing circuit for resetting said disconnect circuit when the telephone is placed back in the on-hook state.   
     
     
       25. A method for preventing a telephone from remaining off-hook and inactive comprising: detecting a signal sent to said telephone from said system when said telephone is in both an off-hook and inactive condition, and   producing an signal in response to said off-hook and inactive condition.   
     
     
       26. Method of claim 25 further comprising: removing said off-hook condition when said telephone in said off-hook and inactive conditions are detected.   
     
     
       27. Method for preventing a telephone from remaining off-hook and inactive comprising: detecting when said telephone is in both an off-hook condition and an inactive condition, and   removing said off hook condition.